Digital Video Broadcast (DVB) transmission standards have been developed in order to support the emergence of digital television. As illustrated in prior art FIG. 1, the DVB signal is sent via an analog carrier and received by a tuner. The tuner receives the transmitted analog signal and provides an analog representation of the signal to a demodulator portion. The demodulator portion converts the analog signal into its digital format. The digital signal provided by the demodulator is in a compressed MPEG 2 format. The compressed MPEG 2 format is referred to as a transport stream. The transport stream from the demodulator comprises a plurality of packets. Each of the transport stream packets comprises one synchronization byte, followed by one of 187 data bytes or 187 data bytes plus 16 extra bytes depending on the format. The resulting transmission stream packets have a total byte size of one of 188 bytes, or 204 bytes.
The data contained within each packet of the transmission stream can represent video data, audio data, system data, and other user data such as programming information. In other words, more than just video data is provided within the transmission stream. For example, user guides indicating channel selection information or stock market information could be included within a transmission stream packet. Because the transport stream data is contained in a compressed format, when video is being transmitted, there is not a one-to-one correspondence between the actual bytes being transmitted in the transport stream and the pixels which the data represents. Because the data is compressed, one packet of transmission stream data can represent varying numbers of pixels in a video system.
A transport demultiplexor receives the digital transport stream as illustrated in prior art FIG. 1. The transport demultiplexor is capable of routing the individual components represented within the transport stream to the respective clients. In other words, audio data could be provided to an audio client while video data would be provided to a video client. For example, the transport demultiplexor can route data by providing address information to the PCI bridge of FIG. 1.
Also illustrated in the prior art of FIG. 1 is a Peripheral Component Interconnect (PCI) bus supporting conventional computer-type peripherals. Connected to the PCI bus of FIG. 1 are a memory, a Central Processor Unit (CPU), and a video adapter. In order to support the reception and subsequent transmission of the transport stream to one of the system components, such as to the memory or the video adapter, a converter/PCI bridge has been used. The converter portion is necessary in order to change the transport stream into data packets capable of being transmitted across a system bus, such as through the PCI bridge. Such a conversion would require converting the 188-byte packet of the transport stream into 32-bit or 64-bit wide words of information and transporting the words to memory or the video adapter across the PCI bus.
In order to provide data to the video adapter of the prior art, it is necessary for separate printed circuit boards to be used to implement the transport stream converter and video adapter. Separate boards allow a PCI interface to the video memory associated with the video adapter. Separate board increase overall system costs. In addition to increasing overall system costs, the data stream requires approximately 5 Mbytes of PCI bandwidth, thereby limiting the bandwidth available to other system resources. In addition, when analog video is received and digitized (not illustrated), by the prior art system the PCI band data bandwidth is approximately 25 Mbytes.
Another proposed method for receiving DVB data was to use the side port of a video graphics adapter in order to receive the transport stream information. However, the video side port is designed to only receive uncompressed digital video instead of compressed MPEG transport stream. A format conversion chip is needed between the DVB demodulator output and video side port to convert a transport stream into a compatible ITU-656 ancillary stream (digital video or data format) like format. This will add cost to system implementation. Another problem is that the data in the transport stream is not fully compliant with ITU-656 data. (Values such as 00 and FF are not allowed in an ITU-656 stream but allowed in a transport stream. So this implementation cannot work if the video side port is strictly designed for ITU-656 data streams.)
Therefore, a method and apparatus, which overcome the problems of the prior art, would be advantageous.